Rotary compressor

ABSTRACT

A rotary compressor having front, and rear housings positioned at the ends of a hollow shell, a horizontal cylinder disposed in the shell and having pressure plates attached to the front and rear ends thereof and further comprising a front housing means interposed between the front housing and the front pressure plate for defining a first front chamber connected by fluid passage means to said inlet port, between the inner wall of said front housing and the outer wall of said front housing means, and a second front chamber connected by fluid passage means to said suction chambers of said cylinder, between the inner wall of said front housing means and the outer face of said front pressure plate, said front housing means having a through-hole to connect said first and second front chambers, and channels adjacent to said oil reservoir to connect said first and second front chambers to said oil reservoir, and; A REAR HOUSING MEANS INTERPOSED BETWEEN THE REAR HOUSING AND THE REAR PRESSURE PLATE FOR DEFINING A FIRST REAR CHAMBER CONNECTED FLUID PASSAGE MEANS TO SAID INLET PORT, BETWEEN THE INNER WALL OF SAID REAR HOUSING AND THE OUTER WALL OF SAID REAR HOUSING MEANS, AND A SECOND REAR CHAMBER BY FLUID PASSAGE MEANS CONNECTED TO SAID SUCTION CHAMBERS OF SAID CYLINDER, BETWEEN THE INNER WALL OF SAID REAR HOUSING MEANS AND THE OUTER FACE OF SAID REAR PRESSURE PLATE, SAID REAR HOUSING MEANS HAVING A THROUGH-HOLE TO CONNECT SAID FIRST AND SECOND REAR CHAMBERS, AND CHANNELS ADJACENT TO SAID OIL RESERVOIR TO CONNECT SAID FIRST AND SECOND REAR CHAMBERS TO SAID OIL RESERVOIR.

ilnited States Patent Nakayama et a].

[ ROTARY COMPRESSOR [75] Inventors: Shozo Nakayama; Masayuki Kurahashi, both of Kariya; Tuneo Sugiura, Hekinan, all of Japan [73] Assignee: Kabushiki Kaisha Toyoda Jidoshokki Seisakusho, Kariya-shi, Japan [22] Filed: June 20, 1973 [21] Appl. No.: 371,822

[30] Foreign Application Priority Data July 27, 1972 Japan 47-88852 [52] US. Cl 418/100, 55/467, 62/469, 417/269 [51] Int. CL... F04c 29/02, F25b 43/02, BOld 45/00 [58] Field of Search 55/182, 434, 467, 471, 55/DIG. l4; 62/468-471; 417/269; 418/100 [56] References Cited UNITED STATES PATENTS 1,878,403 9/1932 Kagi 62/470 2,677,944 5/l954 Ruff 62/468 3,312,387 4/1967 Cassidy et al 418/100 3,352,485 11/1967 417/269 3,676,024 7/1972 62/469 3,730,648 5/1973 Komiya 4'17/269 Primary Examiner-William L. Freeh Assistant Examiner-G. P. LaPointe ABSTRACT positioned at the ends of a hollow shell, a horizontal cylinder disposed in the shell and having pressure plates attached to the front and rear ends thereof and further comprising a front housing means interposed between the front housing and the front pressure plate for defining a first front chamber connected by fluid passage means to said inlet port, between the inner wall of said front housing and the outer wall of said front housing means, and a second front chamber connected by fluid passage means to said suction chambers of said cylinder, between the inner wall of said front housing means and the outer face of said front pressure plate, said front housing means having a through-hole to connect said first and second front chambers, and channels adjacent to said oil reservoir to connect said first and second front chambers to said oil reservoir, and;

a rear housing means interposed between the rear housing and the rear pressure plate for defining a first rear chamber connected fluid passage means to said inlet port, between the inner wall of said rear housing and the outer wall of said rear housing means, and a second rear chamber by fluid passage means connected to said suction chambers of said cylinder, between the inner wall of said rear housing means and the outer face of said rear pressure plate, said rear housing means having a through-hole to connect said first and second rear chambers, and channels adjacent to said oil reservoir to connect said first and second rear chambers to said oil reservoir.

10 Claims, 10 Drawing Figures PATENTEDSEP 31w 3.883.318

sum 10rd FROM F g- EVAPORATOR I!) 7 TO CONDENSER PATENTED 31974 I 3.833.318

sum ear 8 F ROM EVAPORATOR PATENTED 31974 SHEET 3 OF 8 ROTARY COMPRESSOR The present invention relates to a rotary compressor having slidable vanes, which is conveniently applied for aircooling of the vehicle and more particularly, relates to a specific arrangement within such rotary compressor as having a horizontal axially extending hollow shell defining an outermost casing which has a lubricant reservoir at the lower-most portion therein and an inlet port at an upper portion thereof for introducing refrigerant gas to be compressed, front and rear housings positioned at ends of the hollow shell, a horizontal cylinder stationarily disposed in the shell and having pressure plates attached to front and rear ends thereof to define a closed room within the cylinder, and a rotor eccentric and rotatable within the closed room of the cylinder and provided with a number of radial slots for slidably inserting vanes therein whereby the cylinder and the rotor define a space between the inner and outer surfaces thereof for compressing the refrigerating gas introduced therein, the space being separable by said vanes of the rotor into gas-tight suction chambers in fluid communication with the inlet port of the hollow shell and gas-tight compression chambers in fluid communication with to an outlet port of the compressor for discharging the compressed refrigerating gas.

Japanese Utility Model Registration No. 903,216, published June 8, 1970, discloses a type of rotary compressor having slidable vanes, in which there is provided a recess which is formed in an outer wall section of the cylinder including a wall portion facing the refrigerant inlet provided in the outermost shell so as to extend along the cimcumference of the cylinder while having an axial width larger than the diameter of the inlet. Thus, the recess provides a refrigerant suction space between the outer wall of the cylinder and the inner wall of the shell. In the compressor, there are also provided several grooves in the outer wall of the cylinder for guiding oils separated from the returned refrigerants into the oil chamber positioned at the lowermost portion of the compressor. The above-mentioned space between the cylinder wall and the shell wall is fluidly communicated with the compressing chamber within the cylinder through circumferentially extending suction inlet ports formed in both sides of the recess of the cylinder. In this type of rotary compressor, however, the oil separating operation effected while the refrigerant is flowing from the refrigerant inlet to the compressing chamber is insufficient and, as a result, oil is left in the refrigerant which enters the compressing chamber. This fact reduces the volume of refrigerant occupying the compressing chamber and, accordingly, the discharge volume of the refrigerant from the chamber at every compression. As a result, the compressing efficiency as well as air-cooling efficiency of the rotary compressor is reduced.

A principal object of the present invention is to provide a rotary compressor having slidable vanes which can eliminate the above-mentioned objectionable feature of the known compressor, and in which refrigerants returned from an evaporator into the cylinder of the compressor can undergo repeated oil separating operations for almost entirely separating oil content in the returned refrigerant while they are flowing from the inlet for the compressor into the compressing chamber within the cylinder, in order to raise compression efficiency and accordingly, air-cooling efficiency of the compressor.

According to one of the features of the present invention, the rotary compressor mentioned in the beginning of the present disclosure is characterized in that there are further provided front housing means interposed between the front housing and the front pressure plate for defining a first front chamber in fluid communication with the inlet port, between the inner wall of said front housing and the outer wall of said front housing means, and a second front chamber in fluid communication with the suction chambers of said cylinder, between the inner wall of said front housing means and the outer face of said front pressure plate, said front housing means having a through-hole thereby to. connect said first and second front chambers, and channels adjacent to said oil reservoir to connect said first and second front chambers to said oil reservoir, and;

a rear housing means interposed between the rear housing and the rear pressure plate for defining a first rear chamber in fluid communication with said inlet port, between the inner wall of said rear housing and the outer wall of said rear housing means, and a second rear chamber in fluid communication with connected to said suction chambers of said cylinder, between the inner wall of said rear housing means and the outer face of said rear pressure plate, said rear housing means having a throughhole thereby to connect said first and second chambers, and channels adjacent to said oil reservoir to connect said first and second rear chambers to said oil reservoir.

The other objects and advantages of the present invention will be more readily understood from the ensuing description with reference to a preferred embodiment as shown in the accompanying drawings wherein:

FIGS. 1 and 2 are outermost views of the axially opposing ends of a rotary compressor according to the preferred embodiment of the present invention;

FIG. 3 is a cross sectional view along a vertical plane between the opposing ends shown in FIGS. 1 and 2;

FIG. 4 is a longitudinal cross sectional view along the line X, X of FIG. 3;

FIG. 5 is a longitudinal cross sectional view along the line X"! X Of FIG. 6 is a front view of a rear pressure plate employed in the rotary compressor of FIG. 1;

FIGS. 7 and 8 are rear and front views of a rear pressure housing of the rotary compressor of FIG. 1;

FIGS. 9 and 10 are rear and front views of a front pressure housing of the rotary compressor of FIG. 1.

FIGS. 1 and 2 show both ends of a rotary compressor according to a preferred embodiment of the present invention, which includes a longitudinal axis and said both ends face each other at both ends of said axis. Returned refrigerants from an evaporator (refer to FIGS. 1 and 2) of an air-cooling circuit flow into the rotary. compressor through an inlet, and after being compressed therein, are delivered through an outlet and to a condenser in the air-cooling circuits as shown by an arrow labeled to condenser in FIGS. 1 and 2. l0 and 2 respectively show a drive shaft along the longitudinal axis and an oil reservoir which is provided at the bottom of this compressor.

Referring now to FIGS. 3 thru 10, the structure, its operation, and the various advantages of the preferred embodiment shown in FIGS. 1 and 2 will be described in detail. A hollow shell 1 extending longitudinally and provided with an oil reservoir 2 in the lower portion thereof, is closed by respectively fitting front and rear housings 8 and 9 in the openings of its front and rear end portions. Cylinder 3 is stationarily fitted into shell 1, the front and rear ends of said cylinder being closed by pressure plates 4 and 5. Front and rear pressure housings 6 and 7 are placed between said housing 8 and pressure plate 4, and housing 9 and pressure plate 5, respectively. Refrigerant inlet passage 19 is formed by a part of the space between individual inner walls of shell 1, housing 8 and housing 9, and individual outer walls of cylinder 3, pressure plates 4, and pressure housings 6 and 7. One end of said passage 19 is for the passage of fluids connected to a first front chamber 17 defined by the space between the inner side wall of front housing 8 and the outer side wall of front pressure housing 6 through a recess 19a of pressure plate 4 and a recess 19c of pressure housing 6. The other end of said passage 19 is connected for the passage of fluids to a first rear chamber 18 defined by the space between the inner side wall of rear housing 9 and the outer side wall of rear pressure housing 7 through a recess 19b of pressure plate 5 and a recess 19d of pressure housing 7. The sectional areas of both said first chambers are constructed so as to be larger than that of said refrigerant inlet passage 19. A second front chamber 22 is defined by the space between the inner side wall of pressure housing 6 and the outer side wall of pressure plate 4, and a second rear chamber 23 is defined by the space between the inner side wall of pressure housing 7 and the outer side wall of pressure plate 5. The first front chamber 17 and the second front chamber 22, and the first rear chamber 18 and the second rear chamber 23 communicate with each other by through-holes 24 and 25, respectively. Holes 24 and 25 are respectively perforated through the pressure housings 6 and 7 at a position above the center axes of said pressure housings and as distant as possible from the passage 19 (refer to FIGS. 7 thru Sectional areas of the two first chambers 17 and 18 are constructed so as to be larger than those of the two second chambers 22 and 23, which are, in turn, larger than those of the two upper through-holes 24 and 25.

Alternative holes 28 and 29 are respectively perforated through pressure plates 4 and 5, at different positions from said holes 24 and 25, and communicating passages between second chambers 22 and 23 and a gas-tight chamber 35. The lower portions of first chambers 17 and 18, and of second chambers 22 and 23 are provided with guide channels 20, 21, 34 and 37 to discharge lubricating oils separated from the refrigerants by these chambers into oil reservoir 2.

Inlet 26 provided near the center of shell 1 meets at right angles with refrigerant inlet passage 19, and drive shaft 10 is rotatably positioned slightly eccentrically to the axis of cylinder 3 and supported by said housings and also, for example, by bearings 11 and 12. The drive shaft 10 mounts a rotor 13 thereon so that rotor 13 is housed in the cylinder 3. The inner peripheral wall surface of said cylinder 3 associates with the outer peripheral wall surface of rotor 13 to define a space forming a gas-tight arch shaped chamber 35 (refer to FIG. 3). Said gas-tight chamber 35 is separable, by a plurality of slidable leaf vanes fitted into a corresponding number of vane channels 14 formed radially around the rotor 13, into several chambers, as shown for example in FIG. 3. It will be seen that gas-tight chambers 35A and 35B are located on the inlet side, and communicate with said holes 28 and 29 (refer to FIG. 4) in order to suck the refrigerant therethrough, and gas-tight chambers 35C and 35D are located on the compression side and communicate with an outlet hole 27 in the pressure plate 5 (refer to FIG. 6), and the chamber positioned between the chamber 35B and the chamber 35C is an intermediate chamber between the inlet side and the outlet side.

Numerals 31 and 32 indicate channels for directing oil in the reservoir 2 to various moving parts in the compressor in order to lubricate the parts. Numeral 33 indicates a pump for suction of the oil in the reservoir 2 through the channels 31 and 32. The pump 33 is connected to the drive shaft 10 and is operable upon rotation of the drive shaft 10.

The operations and advantages of a rotary compressor according to this invention will now be explained in detail.

Gaseous refrigerants evaporated through an evaporator (not shown) are returned to the compressor after having circulated in the predetermined air-cooling circuits. In the process, the returned refrigerants are directly led to a refrigerant inlet passage 19 through inlet 26 extending through the shell 1. Upon entering inlet passage 19 the refrigerants are divided into two branches by flowing into the front and rear sections of said passage 19. Thus, it should be noted that a first oil separating operation is accomplished by inertia, since the refrigerants are forced to change direction at an angle of substantially The diverged streams of refrigerant pass in opposite directions through the refrigerant inlet passage 19, and reach the two first chambers 17 and 18, respectively, wherein the refrigerants are directed to the bottoms of said chambers 17 and 18 through recesses 19c and 19d formed in the peripheries of pressure housings 6 and 7, as shown by arrows in FIG. 4. The speeds of the refrigerants will decrease at this time because the sectional area of each of the chambers 17 and 18 is larger than that of the passage 19. As a result of this decrease in speed, relatively heavy oil drops contained and floating in the refrigerants are separated by the force of gravity. That is, a second oil separating operation is accomplished here. The separated lubricating oils drop in the first chambers 17 and 18, and flow into the oil reservoir 2 through guide channels 20 and 21 provided at the lower portions of the first chambers 17 and 18, respectively. Meanwhile, the refrigerants separated from the heavy oil drops are introduced into the two second chambers 22 and 23, upper through-holes 24 and 25 of pressure housings 6 and 7, the sectional areas of the holes being smaller than that of the inlet passage 19. Here, it should be noted that the refrigerants reaching the bottoms of the chambers 17 and 18 rise to the upper through-holes 24 and 25. This increases the length of time that the refrigerants remain within the first chambers 17 and 18 and, as a result, the second oil separating operation is prolonged so as to increase the separation of oil. The speeds of the refrigerants in the second chambers 22 and 23 will again decrease since the sectional areas of each of the second chambers 22 and 23 are larger than those of said holes 24 and 25. Accordingly, practically all the oil drops still remaining in the refrigerants are separated. That is, a third oil separating operation is accomplished here. The separated lubricating oils drop into the oil reservoir 2 through guide channel 34 and another channel (not shown) provided at the lower portion of the second chambers 22 and 23 respectively.

The refrigerants in the second chambers 22 and 23 with their oil content removed by the above three oil separating operations are delivered toward the center portion of said gas-tight chambers 35A and 35B (refer to FIG. 3) on the inlet side, from the front and rear sides of the chamber 35, through arch shaped holes 28 and 29 (refer to FIG. 6) perforated through pressure plates 4 and 5. Refrigerants reaching gas-tight chambers 35A and 35B on the inlet side are rotated to gastight chambers 35C and 35D (refer to FIG. 3) on the outlet side, during which time said refrigerants are compressed in said chambers. This is because said gastight chambers are gradually decreased in volume from the inlet side to the outlet side, with revolution of the rotor 13. Refrigerants, then, are delivered to a condenser through the outlet hole 27 and an outlet 36 provided in pressure plate 5 and rear pressure housing 7, respectively. In this embodiment, there is no danger that lubricating oils separated by said first chambers 17 and 18, and by said second chambers 22 and 23 may be entrained up in refrigerant flows and respectively enter into the second chambers 22 and 23, and gastight chamber 35. This is because the holes 24, 25, 28 and 29 are positioned in the upper portions of said two first and two second chambers. Said separated lubricating oils are expelled into the oil reservoir 2 through their own guide channels. In addition, there is also no danger that lubricating oils separated by said inlet passage 19 may be entrained up in refrigerant flows and enter into the second chambers 22 and 23 and gas-tight chamber 35, because parts of said separated lubricating oils drop into the oil reservoir 2 along the peripheral surface of cylinder 3, and the remainder enter into the first chambers 17 and 18 to be expelled into the oil reservoir 2 through guide channels and 21. As the inlet refrigerant passages described in this embodiment contain numerous curves and corners and alternately changing sectional areas, it is possible to further increase the effectiveness of the oil separating operations by providing additional projections in the passage ways of the inlet refrigerants.

As described heretofore, inlet refrigerants change direction to the right and left, since inlet 26 meets at right angles with refrigerant inlet passage 19. As a result of this, the first oil separating operation can be accomplished by inertia. The second and the third oil separating operations can be accomplished by said first chambers and said second chambers. Thus, this invention allows the oil content contained in inlet refrigerants to be repeatedly separated by these several oil separating operations. From this fact, this invention can significantly obviate the shortcoming of known compressors that only a small volume of pure refrigerant contained in the refrigerants can enter into said chamber 35, because the volume of pure refrigerant is limited by the large volume of oil not compressed.

Further, this invention can also achieve an increase in the volume to be sucked in without changing the volume of the inlet chamber, thereby attaining a remarkable increase in suction efficiency.

Refrigerants are separated from the oil flow toward the center of gas-tight chambers on the inlet side from both side ends of the chambers. Consequently, the refrigerants from both directions will collide with each other at approximately the center portion of gas-tight chambers on the inlet side, and their kinetic energy is thereby changed to heat energy promoting the rise of gas pressure.

Further, these refrigerants with raised pressure may be mechanically compressed again by the revolution of the rotor to raise the gas pressure further. Therefore, this invention also provides an increased air-cooling and heating capability over the prior art compressor. Also, in accordance with the concept of the present invention, several small oil separation chambers are separately disposed in place of provision of a single voluminous oil separation chamber in the known compressors.

As a result, the present invention allows appropriate distribution of small oil separation chambers in a predesigned space provided for an assembled compressor and, therefore, a compressor which requires a relatively small installation space, can be provided.

What is claimed is:

1. In a rotary compressor having a horizontal axially extending hollow shell defining an outermost casing which has a lubricant reservoir at the lowermost'portion therein and an inlet port at an upper portion thereof for introducing refrigerant gas to be compressed, front and rear housings positioned at ends of the hollow shell, a horizontal cylinder stationarily disposed in the shell and having pressure plates attached to front and rear ends thereof to define a closed room within the cylinder, and a rotor eccentric and rotatable within the closed room of the cylinder and provided with a number of radial slots for slidably inserting vanes therein whereby the cylinder and the rotor define a space between the inner and outer surfaces thereof for compressing the refrigerating gas introduced therein, said space being separable by said vanes of the rotor into gas-tight suction chambers fluidly connected to the inlet port of the hollow shell and gas-tight compression chambers fluidly connected to an outlet port of the compressor for discharging the compressed refrigerating gas, the improvement comprising:

a front housing means interposed between a front housing and the front pressure plate for defining a first front chamber fluidly connected to said inlet port, between the inner wall of said front housing and the outer wall of said front housing means, and a second front chamber fluidly connected to said suction chambers of said cylinder, between the inner wall of said front housing means and the outer face of said front pressure plate, said front housing means having a through-hole to connect said first and second front chambers, and channels adjacent to said oil reservoir to connect said first and second front chambers to said oil reservoir,

and; v

a rear housing means interposed between the rear housing and the rear pressure plate for defining a first rear chamber fluidly connected to said inlet port, between the inner wall of said rear housing and the outer wall of said rear housing means, and a second rear chamber fluidly connected to said suction chambers of said cylinder, between the inner wall of said rear housing means and the outer face of said rear pressure plate, said rear housing means having a through-hole to connect said first and second rear chambers, and channels adjacent to said oil reservoir to connect said first and second rear chambers to said oil reservoir.

2. A rotary compressor as defined in claim 1, further characterized by passage means defined by the inner walls of said hollow shell and said front and rear housing, and the outer walls of said cylinder, said front and rear pressure plates, and said front and rear housing means, said passage means providing an axial fluid connection between said first front and rear chambers while being connected to said inlet port whereby the flow of said refrigerant gas introduced from said inlet port is divided into two branches in opposite directions reaching said respective first chambers by being changed by an angle of substantially 90.

3. A rotary compressor as defined in claim 2, wherein the connection of said passage means to said inlet port is provided at one half of the substantial length of said passage means.

4. A rotary compressor as defined in claim 2, wherein said front and rear housing means have recesses at a portion of the periphery of said housing means, respectively, thereby to direct said refrigerant gas from said passage means toward the bottoms of said frist front and rear chambers.

5. A rotary compressor as defined in claim 4, wherein said through-holes of said front and rear housing means are provided adjacent to the tops of said respective first chambers.

6. A rotary compressor as defined in claim 4, wherein respective sectional areas of said first chambers taken perpendicular to the direction of said refrigerant gas is larger than the sectional area of said passage means taken perpendicular to the direction of said refrigerant gas flowing in said passage means.

7. A rotary compressor as defined in claim 2, wherein said two branches of the refrigerant gas are introduced into the end of said compressing chamber through inlet holes of said respective pressure plates, said inlet holes directing said refrigerant gas branches to collide with each other at approximately the center portion of said compressing chamber.

8. A rotary compressor as defined in claim 1, wherein said front housing means provide a housing for a bearing means supporting said rotor.

9. A rotary compressor as defined in claim 1, wherein said second front and rear chambers have respective vertically sectional areas larger than the opening areas of the through-holes of said front and rear housing means.

10. A rotary compressor as defined in claim 1, wherein said second front and rear chambers are fluidly connected to said suction chambers through-holes perforated in said pressure plates respectively, and wherein said through-holes of said front and rear housing means and said holes of said pressure plates are circumferentially out of alignment, with respect to the center of said shaft.

"UNITED STATES PATENT OFFICE CERTIFICATE. OF CORRECTION Patent No. 3, 833,318 Dated September 3, 1974 TUNED SUGIU'RA Q Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

( )n the title page, column 2, line 20, after "connected" insert by I Column 1, line 25, cancel "to".

Column 3, line 14, before "for" insert connected line 48, before "communicating" add provide Column 5, lines 39, 41, 46, 49, so and 63, change. "fluidly. connected to" to in fluid communication with Column 7, line 18, change "at one half of the substantial" to a poi'it midway along the I line 24, change "frist" to first Column 8, lines 22 and 23, change fluidly connected to" to in fluid communication with Signed and sealed this 11th day of March 1975.

(SEAL) Attest:

w v v, I c. MARSHALL DANN v RUTH C. MASON Coimix'fssioner of Patents Attesting Officer and Trademarks 

1. In a rotary compressor having a horizontal axially extending hollow shell defining an outermost casing which has a lubricant reservoir at the lowermost portion therein and an inlet port at an upper portion thereof for introducing refrigerant gas to be compressed, front and rear housings positioned at ends of the hollow shell, a horizontal cylinder stationarily disposed in the shell and having pressure plates attached to front and rear ends thereof to define a closed room within the cylinder, and a rotor eccentric and rotatable within the closed room of the cylinder and provided with a number of radial slots for slidably inserting vanes therein whereby the cylinder and the rotor define a space between the inner and outer surfaces thereof for compressing the refrigerating gas introduced therein, said space being separable by said vanes of the rotor into gas-tight suction chambers fluidly connected to the inlet port of the hollow shell and gastight compression chambers fluidly connected to an outlet port of the compressor for discharging the compressed refrigerating gas, the improvement comprising: a front housing means interposed between a front housing and the front pressure plate for defining a first front chamber fluidly connected to said inlet port, between the inner wall of said front housing and the outer wall of said front housing means, and a second front chamber fluidly connected to said suction chambers of said cylinder, between the inner wall of said front housing means and the outer face of said front pressure plate, said front housing means having a through-hole to connect said first and second front chambers, and channels adjacent to said oil reservoir to connect said first and second front chambers to said oil reservoir, and; a rear housing means interposed between the rear housing and the rear pressure plate for defining a first rear chamber fluidly connected to said inlet port, between the inner wall of said rear housing and the outer wall of said rear housing means, and a second rear chamber fluidly connected to said suction chambers of said cylinder, between the inner wall of said rear housing means and the outer face of said rear pressure plate, said rear housing means having a through-hole to connect said first and second rear chambers, and channels adjacent to said oil reservoir to connect said first and second rear chambers to said oil reservoir.
 2. A rotary compressor as defined in claim 1, further characterized by passage means defined by the inner walls of said hollow shell and said front and rear housing, and the outer walls of said cylinder, said front and rear pressure plates, and said front and rear housing means, said passage means providing an axial fluid connection between said first front and rear chambers while being connected to said inlet port whereby the flow of said refrigerant gas introduced from said inlet port is divided into two branches in opposite directions reaching said respective first chambers by being changed by an angle of substaNtially 90*.
 3. A rotary compressor as defined in claim 2, wherein the connection of said passage means to said inlet port is provided at one half of the substantial length of said passage means.
 4. A rotary compressor as defined in claim 2, wherein said front and rear housing means have recesses at a portion of the periphery of said housing means, respectively, thereby to direct said refrigerant gas from said passage means toward the bottoms of said frist front and rear chambers.
 5. A rotary compressor as defined in claim 4, wherein said through-holes of said front and rear housing means are provided adjacent to the tops of said respective first chambers.
 6. A rotary compressor as defined in claim 4, wherein respective sectional areas of said first chambers taken perpendicular to the direction of said refrigerant gas is larger than the sectional area of said passage means taken perpendicular to the direction of said refrigerant gas flowing in said passage means.
 7. A rotary compressor as defined in claim 2, wherein said two branches of the refrigerant gas are introduced into the end of said compressing chamber through inlet holes of said respective pressure plates, said inlet holes directing said refrigerant gas branches to collide with each other at approximately the center portion of said compressing chamber.
 8. A rotary compressor as defined in claim 1, wherein said front housing means provide a housing for a bearing means supporting said rotor.
 9. A rotary compressor as defined in claim 1, wherein said second front and rear chambers have respective vertically sectional areas larger than the opening areas of the through-holes of said front and rear housing means.
 10. A rotary compressor as defined in claim 1, wherein said second front and rear chambers are fluidly connected to said suction chambers through-holes perforated in said pressure plates respectively, and wherein said through-holes of said front and rear housing means and said holes of said pressure plates are circumferentially out of alignment, with respect to the center of said shaft. 